Measurement of physical phenomenon may be accomplished by converting the phenomenon to be measured to a physical change to a fiber Bragg grating. A Bragg grating is a series of modulations of internal refractive index which are written on the inner core of an optical fiber. These gratings may then be coupled to a structure to be characterized to generate a measurement of strain or temperature. Any physical phenomenon which may be converted to a grating length or index change may be used to accomplish the measurement of the underlying phenomenon. In a typical use, the Bragg grating is illuminated by a broadband source such that multiple Bragg gratings may be interrogated, and each of these gratings illuminated by the broadband source such that each grating reflects a particular wavelength which may be measured to determine the strain or temperature applied to each grating. When the relationship between wavelength and parameter is characterized or understood, the individual reflected wavelengths may be ready by a wavelength interrogator, and the change in wavelength can be converted to a physical value. A prior art tunable grating may be seen in U.S. Pat. No. 7,133,582 by Moslehi et al, and prior art cascade wavelength interrogators are known from U.S. Pat. No. 7,127,132, 6,895,132, 6,788,835, 6,751,367, and 6,597,822 by Moslehi et al, which disclosures are hereby incorporated by reference.